بهسازی خاک ماسه ای سست با بالشتک دانه ای و ستون سنگی در سلول واحد

نوع مقاله : مقاله کامل پژوهشی

نویسندگان

1 دانشکده مهندسی عمران، دانشگاه یزد

2 دانشکده مهندسی عمران، دانشگاه صنعتی خواجه نصیرالدین طوسی

3 دانشکده مهندسی عمران، دانشگاه اصفهان

چکیده

در این تحقیق تاثیر بالشتک دانه‌ای مسلح با ژئوگرید، ستون سنگی و ترکیب این روش‌ها بر رفتار نمونه‌های خاک ماسه‌ای سست در سلول واحد با انجام آزمون‌های آزمایشگاهی مورد بررسی قرار گرفت. با توجه به اینکه تا کنون در مطالعات تجربی به گسیختگی مسلح‌کننده در بالشتک دانه‌ای مسلح پرداخته نشده، روشی نوین جهت نصب ژئوگرید در سلول واحد به ‌کار رفته تا امکان گسیختگی مسلح‌کننده تحت تنش‌های وارده محقق گردد. طی مطالعات پارامتریک مدل‌های فیزیکی، تاثیر تغییر آرایش مسلح‌کننده ژئوگرید شامل تعداد و محل قرارگیری آن در بالشتک‌ با ضخامت‌های متغیر مطالعه شده و بهترین محل قرارگیری ژئوگرید تک و دو لایه در ضخامت بالشتک گردید. از دیگر اهداف مورد بررسی‌، آشکارسازی مکانیسم گسیختگی لایه‌های ژئوگرید و اثر آن بر ویژگی‌های بارپذیری و نشست نمونه‌های بهسازی شده با ستون سنگی و بدون ستون بوده است. در مقایسه با بستر ماسه‌ای غیر مسلح، افزایش 9/7 و 38/11 برابری نسبت باربری در شرایط استفاده از بالشتک دانه‌ای مسلح با یک و دو لایه ژئوگرید (در آرایش بهینه) واقع بر بستر بهسازی شده با ستون سنگی مشاهده شده است. در ادامه، از طریق شبیه‌سازی عددی در نرم‌افزار المان محدودV 8.6 PLAXIS 2D، ضخامت بهینه بالشتک غیر مسلح و مسلح، 16/0 برابر قطر پی تعیین گردیده و تغییرات نسبت تمرکز تنش در ستون سنگی در مدل‌های مختلف مورد ارزیابی قرار گرفته است. مقایسه آرایش‌های تسلیح بالشتک نشان می‌دهد هر چه ژئوگرید به زیر پی نزدیک‌تر باشد نقش موثرتری در افزایش بارپذیری، کاهش نشست و کاهش نسبت تمرکز تنش در ستون سنگی خواهد داشت.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Investigation of Loose Sandy Soil Improvement with Granular Blanket and Stone Column in a Unit Cell

نویسندگان [English]

  • Ali Shahmandi 1
  • Kazem Barkhordari 1
  • Mahmoud Ghazavi 2
  • Mahmoud Hashemi 3
1 Faculty of Civil Engineering, University of Yazd, Yazd, Iran
2 Faculty of Civil Engineering, K.N. Toosi University of Technonlogy, Tehran, Iran
3 Faculty of Civil Engineering, University of Isfahan, Isfahan, Iran
چکیده [English]

In this study, the effect of the unreinforced and geogrid-reinforced granular blankets, end-bearing stone columns and the combination of these techniques on the behaviour of loose sand soil models have been investigated through laboratory and numerical simulations. In the models, a stone column from a large group of them with a triangular pattern was simulated in a unit cell. Since the rupture of the geosynthetic reinforcement within the reinforced granular blanket has never been experimentally investigated, a novel method of installing the geogrid reinforcement was used, allowing it to mobilize and ultimately fail under loading. The optimal thickness of the unreinforced and geogrid-reinforced blanket, the optimum layout of the reinforcement within the blanket and the changes in the stress concentration ratio of the stone column in different modelling conditions have been determined. Another objective of the present study is to discover the relationship between the failure of the geogrid layers and the characteristics of load-carrying capacity and settlement of the model tests.

کلیدواژه‌ها [English]

  • Granular blanket
  • Geogrid reinforcement
  • Loose sand bed
  • Stone column
  • Unit cell
Abdi MR, Zandieh AR, “Experimental and numerical analysis of large scale pull out tests conducted on clays reinforced with geogrids encapsulated with coarse material”, Geotextiles and Geomembranes, 2014, 42 (5), 494-504.
Abdullah CH, Edil TB, “Behaviour of geogrid-reinforced load transfer platforms for embankment on rammed aggregate piers”, Geosynthetics International, 2007, 14 (3), 141-153. https://doi.org/10.1680/gein.2007.14.3.141
Abu-Farsakh M, Chen QM, Sharma R, “An experimental evaluation of the behavior of footings on geosynthetic-reinforced sand”, Soils and Foundations, 2013, 53 (2), 335-348.
Akosah S, Chen J, Bao N, “Reinforcement of problematic soils using geotextile encased stone/sand columns”, Arabian Journal of Geosciences, 2022, 15 (1371), 1-21. https://doi.org/10.1007/s12517-022-10561-0
Ali K, Shahu JT, Sharma KG, “Model tests on geosynthetic-reinforcement stone columns: a comparative study”, Geosynthetics International, 2012, 19 (4), 292-305. https://doi.org/10.1680/gein.12.00016
Ali K, Shahu JT, Sharma KG, “Model tests on single and groups of stone columns with different geosynthetic reinforcement arrangement”, Geosynthetics International, 2014, 21 (2), 103-118. https://doi.org/10.1680/gein.14.00002
Alkhorshid NR, Araujo GLS, Palmeira EM, “Consolidation of soft clay foundation improved by geosynthetic-reinforced granular columns: Numerical evaluation”, Journal of Rock Mechanics and Geotechnical Eingineering, 2021, 13 (5), 1173-1181. https://doi.org/10.1016/j.jrmge.2021.09.017
ASTM D2850-03, Standard test method for unconsolidated-undrained triaxial compression test, American Society for Testing and Materials; Pennsylvania, USA, 2003.
ASTM D6637/D6637M-15, Standard test method for determining tensile properties of geogrids by the single or multi-rib tensile method, American Society for Testing and Materials; Pennsylvania, USA, 2015.
Barksdale RD, Bachus C, “Design and construction of stone column volume I, Final Report”, FHWA/RD-83/026; U.S. Department of Transportation/Federal Highway Administration, USA, 1983.
Basudhar PK, Dixit PM, Ghaprure A, Deb K, “Finite element analysis of geotextile-reinforced sand-bed subjected to strip loading”, Geotextile and Geomembrane, 2008, 26 (1), 91-99. https://doi.org/10.1016/j.geotexmem.2007.04.002
Binquet J, Lee KL, “Bearing capacity tests on reinforced earth slabs”, Journal of Geotechnical Engineering, ASCE, 1975, 101 (GT12), 1241-1255.
Buckingham E, “On physically similar systems; illustrations of the use of dimensional equations, Rev. 4, 345”, Physical Review Journals Archive, 1914, 4 (4), 345-376. https://doi.org/10.1103/PhysRev.4.345
Burd HJ, “Analysis of membrane action in reinforced unpaved roads”, Canadian Geotechnical Journal, 1995, 32 (6), 946-956.
Chen JF, Guo XP, Xue JF, Guo PH, “Load behavior of model strip footings on reinforced transparent soils”, Geosynthetic International, 2019, 26 (3), 251-260. https://doi.org/10.1680/jgein.19.00003
Chen QM Abu-Farsakh M, “Ultimate bearing capacity analysis of strip footings on reinforced soil foundation”, Soils and Foundations, 2015, 55 (1), 74-85. https://doi.org/10.1016/j.sandf.2014.12.006
Chen WF, Saleeb AF, “Constitutive Equations for Engineering Materials”, Second Revised Edition, Elsevier Science B.V, New York, USA, 1994.
Dean G, Mera R, “Determination of material properties and parameters required for the simulation of impact performance of plastics using finite element analysis”, National Physical Laboratory (NPL), Middlesex, UK, p. 49. Report No. DEPC-MPR 007, 2004.
Deb K, Chandra S, Basudhar PK, “Response of multi-layer geosynthetic-reinforced bed resting on soft soil with stone columns”, Computers and Geotechnics, 2008, 35 (3), 323-330. https://doi.org/10.1016/j.compgeo.2007.08.004
Deb K, Samadhiya NK, Namdeo JB, “Laboratory model studies on unreinforced and geogrid-reinforced sand bed over stone column-improved soft clay”, Geotextiles and Geomembranes, 2011, 29 (2), 190-196. https://doi.org/10.1016/j.geotexmem.2010.06.004
Debnath P, Dey AK, “Bearing capacity of geogrid-reinforced sand over encased stone columns in soft clay”, Geotextiles and Geomembranes, 2017, 45 (6), 653-664. https://doi.org/10.1016/j.geotexmem.2017.08.006
Ehsaniyamchi A, Ghazavi M, “Short-term and long-term behavior of geosynthetic-reinforced stone columns”, Soils and Foundations, 2019, 59 (5), 1579-1590. https://doi.org/10.1016/j.sandf.2019.07.007
Ehsaniyamchi A, Ghazavi M, “Reinforcement of floating stone columns with spaced reinforcing rings”, Proceedings of the Institution of Civil Engineers-Ground Improvement, 2021, 174 (4), 273-287.  https://doi.org/10.1680/jgrim.19.00090
Elshazly HA, Hafez DH, Mossaad ME, “Reliability of Conventional Settlement Evaluation for Circular Foundations on Stone Columns”, Journal of Geotechnical and Geological Engineering, 2008, 26 (3), 323-334. https://doi.org/10.1007/s10706-007-9169-9
Fakher A, “Research Methods in Geotechnics”, Publication Institute of University of Tehran, Tehran, Iran, 2014.
Fox ZP, “Critical state, dilatancy and particle breakage of mine waste rock”, Ph.D. Dissertation, Colorado State University, Colorado, 2011.
Gharehzadeh Shirazi M, Rashid ASA, Nazir R, Rashid AHA, Horpibulsuk S, “Enhancing the bearing capacity of rigid footing using limited life kenaf geotextile reinforcement”, Journal of Natural Fibers, 2020, 19 (8), 2868-2884.
Ghazavi M, Ehsaniyamchi A, Nazari Afshar J, “Bearing capacity of horizontally layered geosynthetic reinforced stone columns”, Geotextiles and Geomembranes, 2018, 46 (3), 312-318.
Giroud JP, Han J, “Design method for geogrid-reinforced unpaved roads, Part I: theoretical development”, Journal of Geotechnical and Geoenvironmental Engineering, 2004, 130 (8), 776-786. https://doi.org/10.1061/(ASCE)1090-0241(2004)130:8(775)
Gniel J, Bouazza A, “Improvement of soft soils using geogrid encased stone columns”, Geotextiles and Geomembranes, 2009, 27 (3), 167-175. https://doi.org/10.1016/j.geotexmem.2008.11.001
Gouw TL, “Common mistakes on the application of plaxis 2D in analyzing excavation problems”, International Journal of Applied Engineering Research, 2014, 9 (21), 8291-8311.
Gu M, Mo H, Qiu J, Yuan J, Xia Q, “Behavior of floating stone columns reinforced with geogrid encasement in model tests”, Frontiers in Materials, 2022, 9, 1-10. https://doi.org/10.3389/fmats.2022.980851
Guido VA, Chang DK, Sweeney MA, “Comparison of geogrid and geotextile reinforced earth slabs”, Canadian Geotechnical Journal, 1986, 23 (4), 435-440. https://doi.org/10.1139/t86-073
Hamidi M, Lajevardi SH, “Experimental study on the load-carrying capacity of single stone columns”, International Journal of Geosynthetics and Ground Engineering, 2018, 4 (26), 1-10.
        https://doi.org/10.1007/s40891-018-0142-x
Han J, Gabr MA, “Numerical analysis of geosynthetic-reinforced and pile-supported earth platform over soft soil”, Journal of Geotechnical and Geoenvironmental Engineering, 2002, 128 (1), 44-53. https://doi.org/10.1061/(ASCE)1090-0241(2002)128:1(44)
Hasan M, Samadhiya NK, “Experimental and numerical analysis of geosynthetic-reinforced floating granular piles in soft clays”, International Journal of Geosynthetics and Ground Engineering, 2016, 2 (3), 1-13. https://doi.org/10.1007/s40891-016-0062-6
Hataf N, Nabipour N, Sadr A, “Experimental and numerical study on the bearing capacity of encased stone columns”, International Journal of Geo-Engineering, 2020, 11 (4), 1-19.
        https://doi.org/10.1186/s40703-020-00111-6
Hong YS, Wu CS, Yu YS, “Model tests on geotextile-encased granular columns under 1-g and undrained conditions”, Geotextiles and Geomembranes, 2016, 44 (1), 13-27.
Hosamo H, Sliteen I, Ding S, “Numerical analysis of bearing capacity of a ring footing on geogrid reinforced sand”, Buildings, 2021, 11 (2), 1-12. https://doi.org/10.3390/buildings11020068
Hussein MG, Meguid MA, “A three-dimensional finite element approach for modeling biaxial geogrid with application to geogrid-reinforced soils”, Geotextiles and Geomembranes, 2016, 44 (3), 295-307.https://doi.org/10.1016/j.geotexmem.2015.12.004
Iai S, “Similitude for shaking table tests on soil-structure fluid models in 1g gravitational field”, Soils and Foundations, 1989m 29 (1), 105-118. https://doi.org/10.3208/sandf1972.29.105
Imam R, Zarei M, Ghafarian D, “Relative contribution of various deformation mechanisms in the settlement of floating stone column-supported foundations”, Computers and Geotechnics, 2021, (134), 104109. https://doi.org/10.1016/j.compgeo.2021.104109
Kang B, Wang J, Zhou Y, Huang Sh, “Study on bearing capacity and failure mode of multi-layer-encased geosynthetic-encased stone column under dynamic and static Loading”, Sustainability, 2023, 15 (6), 1-18. https://doi.org/10.3390/su15065205
Koerner RM, “Designing with Geosynthetics”, 6th Edition, Volume 1, New Jersey, Prentice Hall, USA, 2005.
Lee KM, Manjunath VR, Dewaikar DM, “Numerical and model studies of strip footing supported by a reinforced granular fill-soft soil system”, Canadian Geotechnical Journal, 1999, 36 (5), 793-806. https://doi.org/10.1139/t99-053
Liu HL, Ng CWW, Fei K, “Performance of a geogrid-reinforced and pile supported highway embankment over soft clay: case study”, Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 2007, 133 (12), 1483-1493. https://doi.org/ 10.1061/(ASCE)1090-0241(2007)133:12(1483)
McCabe BA, Killeen M, “Small stone column groups: mechanisms of deformation at serviceability limit state”, International Journal of Geomechanics, ASCE, 2016, 17 (5), 1-14.
Mehrannia N, Kalantary F, Ganjian N, “Experimental study on soil improvement with stone columns and granular blankets”, Journal of Central South University, 2018, 25 (4), 866-878. https://doi.org/10.1007/s11771-018-3790-z
Mohapatra SR, Rajagopal K, Sharma J, “Direct shear tests on geosynthetic-encased granular columns”, Geotextiles and Geomembranes, 2016, 44 (3), 396-405. https://doi.org/10.1016/j.geotexmem.2016.01.002
Murugesan S, Rajagopal K, “Studies on the Behavior of Single and Group of Geosynthetic Encased Stone Columns”, Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 2010, 136 (1), 129-139.
NAUE GMBH & CO KG, “Naue Products Manual”, Espelkamp, Germany, 2021.
Nayak NV, “Recent advances in ground improvements by stone column”, Proceedings of Indian Geotechnical Conference, IGC-83, Madras, India, December, 1983.
Ramadan EH, Abdel-Naiem MA, Senoon AA, Megally AA, “Stone columns and reinforced sand bed for performance improvement of foundations on soft clay”, International Journal of Advances in Structural and Geotechnical Engineering, 2022, 6 (3), 57-64.
        https://doi.org/10.21608/ASGE.2022.274736
Sarfarazi V, Tabaroei A, Asgari K, “Discrete element modeling of strip footing on geogrid-reinforced soil”, Geomechanics and Engineering, 2022, 29 (4), 435-449. https://doi.org/10.12989/gae.2022.29.4.435
Sexton BG, McCabe BA, Castro J, “Appraising stone column settlement prediction methods using finite element analyses”, Acta Geotechnica, 2013, 9, 993-1011. https://doi.org/10.1007/s11440-013-0260-5
Shahu JT, Madhav MR, Hayashi S, “Analysis of soft ground-granular pile-granular mat system”, Computers and Geotechnics, 2000, 27 (1), 45-62. https://doi.org/10.1016/S0266-352X(00)00004-5
Stoeber JN, “Effects of maximum particle size and sample scaling on the mechanical behavior of mine waste rock: A critical state approach”, Ph.D. Dissertation, Colorado State University, Colorado, 2012.